This invention relates to a catalyst detector for a vehicle, and more particularly to a detector provided in a vehicle to detect loss and deterioration of a catalyst coating for decomposing chemical substances such as ozone (O3) in the ambient air.
Many national or local governments have a variety of regulations on emissions (exhaust gases) from vehicles. For example, In California, United States, there are regulations on emissions of non-methane organic gases (NMOG), carbon monoxides (CO), nitrogen oxides (NOx), and the like. These regulations make it mandatory for manufacturers of vehicles in California to abide by emission standards (maximum permissible quantities stipulated for each vehicle or control limits set at manufactures' average) for NMOG, etc. Accordingly, each manufacturer has been focusing efforts on the development of low emission vehicles (LEV) or zero emission vehicles (ZEV).
Growing public awareness of environmental problems in recent years has been accelerating the trend toward strict emissions control, and tightening the regulations on emissions. On the other hand, some governments provide interim measures for granting the manufacturers some delay in developing new technologies for reduction in exhaust gases. For example, the NMOG emissions control in California, United States provides an NMOG accreditation program with which NMOG credits are granted to manufacturers adopting the direct ozone reduction (DOR) technology in their products and to DOR-using vehicles. To be more specific, photochemical smog (ozone: O3) in the atmosphere results from chemical reactions involving nitrogen oxides and non-methane organic gases in the presence of sunlight (see FIG. 9), and in California, vehicles having means for catalytically decomposing ozone (and cleaning up the air) during driving utilizing the DOR technology and manufacturers producing such vehicles are accredited with reducing amounts of NMOG emissions, and the state government of California is supposed to grant prescribed incentives (NMOG credits) thereto. Accordingly, the manufactures are making attempts to sell vehicles having an ozone decomposing device that uses the DOR techniques. The ozone decomposing devices that provide an ozone decomposing catalytic coating across a surface of the radiator (surfaces of radiator fins) in the vehicles are disclosed, for example, in JP 2001-247017 A and JP 2001-347829 A.
However, ozone decomposing performances of the ozone decomposing devices are subject to change, and decrease with deterioration of catalyst, loss (detachment) of the catalyst coating and the like. Therefore, NMOG credits are supposed to be granted to the vehicles in accordance with ozone decomposing performances thereof measured after 150,000 miles (approx. 241,350 km) of driving. Each manufacturer evaluates ozone decomposing performances after 150,000 miles of driving for each vehicle type and for each vehicle model through testing of various kinds, and submits an application for certification of NMOG credits with the evaluated value or a value lower than the evaluated value to the authority. The ozone decomposing device installed in a new vehicle should fulfill the evaluated value of the performance at the time of submitting the application, but the performance could disadvantageously decrease to a value lower than the value declared in the application before 15,000 miles of driving depending on circumstances (e.g., under rough usage). To take appropriate measures against the above disadvantage, the manufacturers of the vehicles should continuously demonstrate the ozone decomposing performance and durability of the ozone decomposing device throughout the effective period of service life so that maintenance and checkup can be timely carried out. For that purpose, the manufacturers are required to incorporate an on-board diagnostic (OBD) system for monitoring the performance of the ozone decomposing device in each vehicle they ships, so as to guarantee that appropriate control is being exercised on emissions. Therefore, each manufacturer has been developing such on-board diagnostic systems.
The above disclosures refer to methods of detecting loss or deterioration of catalyst coatings using a sensor or the like (as embodied in on-board diagnostic systems), but no specific reference is made to a position of detection (or a location where a sensor is installed) relative to a radiator. The inventors named in the present application have discovered that the position of detection relative to a radiator is critical in accurate detection of decrease in performance of the ozone decomposing device.
The present invention has been made to address the above-discussed disadvantages, and it is an exemplary general object of the present invention to provide a catalyst detector capable of accurately detecting decrease in performance of the ozone decomposing device provided in vehicles.